When deploying undersea fiber optic communication cables, it is frequently necessary to splice or join cable segments together. Examples include assembling lengths of cable long enough to traverse an ocean, or during a cable repair process. When the cable is cut and then rejoined, the structure of the cable and the splice or repair closures must withstand deep ocean hydrostatic pressure (10,000 psi), and the cable/closure dielectric properties must remain stable electrically with insulation from sea ground (.+-.7500 VDC) for an anticipated system life of 25 years.
The prior art teaches the encapsulation of electromechanical cable repair components by molding over the assembly and the cable jacket with a thermoplastic material of similar composition to that of the cable jacket. Once the electromechanical parts are assembled, a premolded stress-free sleeve of thermoplastic material similar in composition to that of the cable jacket is slid over the electromechanical assembly. This assembly is placed in the lower cavity of a mold. The upper mold cavity is bolted to the lower cavity to form an encapsulating mold. The mold is heated to the injection temperature. Injection takes approximately two hours. Upon completion of the injection process, the mold and the overmold material are subjected to a controlled cooling process to restore the injection material to its original composition properties. When the cooling process is complete, the mold is opened and the overmold is inspected.
The overmolding process of the prior art has several infirmities. One is that the entire closure must be heated. Further, the process requires adjunct materials such as clips, gaskets and preforms. Also, the overmolding process of the prior art does not lend itself to welding of internal walls. From 10-20 percent of the molds fail due to contaminants or air bubbles. These joints must then be cut out, replaced and remolded. The total time for the overmolding process from start to finish is on the order of three hours, assuming a good mold.